lci/lib/miniFun/Semantics.ml

module Utility = Utility
open Types;;

Random.self_init ()

let (let*) = Result.bind

let rec evaluate (mem: memory) (command: t_exp) : (permittedValues, error) result =
  match command with
    Integer n -> Ok (IntegerPermitted n)
  | Boolean b -> Ok (BooleanPermitted b)
  | Variable v -> (
      match VariableMap.find_opt v mem.assignments with
        None -> Error (`AbsentAssignment ("The variable " ^ v ^ " is not defined."))
      | Some a -> Ok a
    )
  | Function (xs, _, f) ->
    Ok (FunctionPermitted
          {inputList = xs;
           body = f;
           assignments = mem.assignments;
           recursiveness = None}
       )
  | Application (f, xs) -> (
      let* evalf = evaluate mem f in
      let* funcClosure = (
        match evalf with
          FunctionPermitted ff -> Ok ff
        | IntegerPermitted _ -> Error (`WrongType ("Function is not a function,"
                                                   ^ " it's an integer"))
        | BooleanPermitted _ -> Error (`WrongType ("Function is not a function,"
                                                   ^ " it's a boolean"))
      ) in
      let parmList = List.map (fun k -> evaluate mem k) xs in
      let rec helper m params values =
        match (params, values) with
          (_, []) -> Ok (m, params)
        | ([], _) ->
          Error (`WrongArity ("Function application has arity " ^
                              (List.length funcClosure.inputList
                               |> string_of_int) ^
                              ", but was applied to " ^
                              (List.length xs |> string_of_int) ^
                              " parameters"))
        | (p::tlparams, (Ok v)::tlvalues) -> helper
                                          (VariableMap.add p v m)
                                          tlparams
                                          tlvalues
        | (_, (Error e)::_) -> Error e
      in
      let* (mem2assignments, params) = helper
          funcClosure.assignments
          funcClosure.inputList
          parmList
      in
      let mem2 = (
        match funcClosure.recursiveness with
          None -> {assignments = mem2assignments}
        | Some nameF -> {
            assignments =
              VariableMap.add
                nameF
                (FunctionPermitted funcClosure)
                mem2assignments
          }
      ) in
      match params with
        [] -> evaluate mem2 funcClosure.body
      | _ -> (
          Ok (FunctionPermitted {funcClosure with inputList = params;
                                                  assignments = mem2assignments}))
    )
  | Plus (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    Ok (IntegerPermitted (aval + bval))
  | Minus (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    Ok (IntegerPermitted (aval - bval))
  | Times (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    Ok (IntegerPermitted (aval * bval))

  | Division (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in (
      try
        Ok (IntegerPermitted (aval / bval))
      with Division_by_zero -> Error (`DivisionByZero "Dividing by zero")
    )

  | Modulo (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    Ok (IntegerPermitted (aval mod bval))
  | Power (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    Ok (IntegerPermitted (Utility.pow aval bval))

  | PowerMod (a, b, c) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    let* cval = (
      match evaluate mem c with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    Ok (IntegerPermitted (Utility.powmod aval bval cval))
  | Rand (a) ->
    let* aval = (
      match evaluate mem a with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    )
    in
    Ok (IntegerPermitted (Random.int aval))

  | BAnd (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok BooleanPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an boolean"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok BooleanPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an boolean"))
    )
    in
    Ok (BooleanPermitted (aval && bval))

  | BOr (a, b) ->
    let* aval = (
      match evaluate mem a with
        Ok BooleanPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an boolean"))
    )
    in
    let* bval = (
      match evaluate mem b with
        Ok BooleanPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an boolean"))
    )
    in
    Ok (BooleanPermitted (aval || bval))

  | BNot a ->
    let* aval = (
      match evaluate mem a with
        Ok BooleanPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an boolean"))
    )
    in
    Ok (BooleanPermitted (not aval))

  | Cmp (exp_1, exp_2) ->
    let* exp_1val = match evaluate mem exp_1 with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    in
    let* exp_2val = match evaluate mem exp_2 with
        Ok IntegerPermitted x -> Ok x
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value is not an integer"))
    in
    Ok (BooleanPermitted (exp_1val = exp_2val))

  | CmpLess (exp_1, exp_2) -> (
      let* exp_1val = match evaluate mem exp_1 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      let* exp_2val = match evaluate mem exp_2 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      Ok (BooleanPermitted (exp_1val < exp_2val))
    )
  | CmpLessEq (exp_1, exp_2) -> (
      let* exp_1val = match evaluate mem exp_1 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      let* exp_2val = match evaluate mem exp_2 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      Ok (BooleanPermitted (exp_1val <= exp_2val))
    )
  | CmpGreater (exp_1, exp_2) -> (
      let* exp_1val = match evaluate mem exp_1 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      let* exp_2val = match evaluate mem exp_2 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      Ok (BooleanPermitted (exp_1val > exp_2val))
    )
  | CmpGreaterEq (exp_1, exp_2) -> (
      let* exp_1val = match evaluate mem exp_1 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      let* exp_2val = match evaluate mem exp_2 with
          Ok IntegerPermitted x -> Ok x
        | Error e -> Error e
        | _ -> Error (`WrongType ("Value is not an integer"))
      in
      Ok (BooleanPermitted (exp_1val >= exp_2val))
    )
  | IfThenElse (guard, if_exp, else_exp) ->
    let* bguard = (
      match evaluate mem guard with
        Ok BooleanPermitted b -> Ok b
      | Error e -> Error e
      | _ -> Error (`WrongType ("Value in if guard is not a boolean"))
    ) in
    if bguard then
      evaluate mem if_exp
    else
      evaluate mem else_exp
  | LetIn (x, xval, rest) ->
    let* evalxval = evaluate mem xval in
    let mem2 = {assignments = VariableMap.add x evalxval mem.assignments} in
    evaluate mem2 rest
  | LetFun (f, xs, _, fbody, rest) ->
    let mem2 = {
      assignments =
        VariableMap.add
          f
          (FunctionPermitted
             { inputList = xs;
               body = fbody;
               assignments = mem.assignments;
               recursiveness = Some f})
          mem.assignments}
    in
    evaluate mem2 rest


let reduce (program: t_exp) (iin : int) : (int, error) result =
  let program' = (Application (program, [(Integer iin)])) in
  let mem : memory = {assignments = VariableMap.empty} in
  match (evaluate mem program') with
    Ok IntegerPermitted a -> Ok a
  | _ -> Error (`WrongType ("Main function doesn't return an integer"))